Menopause marks an important transition in females that affects both reproductive and non-reproductive function. The extended period of hypoestrogenicity in post-menopausal women profoundly affects the central nervous system by modifying multiple brain functions, increasing the incidence of neurodegenerative diseases, and increasing the risk of ischemic stroke in older women. Several studies have shown that physiological concentrations of 17beta-estradiol (E2) protect against delayed cell death in stroke models and serve an anti-inflammatory role in the central nervous system (CMS.) To further examine the dynamic and complex relationship between E2, inflammation, and apoptosis during stroke, this proposal will test the hypothesis that physiological concentrations of E2 decrease inflammation leading to apoptotic cell death. This hypothesis will be tested in ovariectomized (OVX) and OVX + E2 - treated C57BL/6J (WT) and inducible nitric oxide synthase knockout (iNOSKO) mice using a model of permanent middle cerebral artery occlusion. Three critical components of the ischemic inflammatory response, i.e. 1) microglial activation, 2) inducible nitric oxide synthase gene expression, and 3) production of cytokines and chemokines, will be measured to determine to determine their ability to potentiate two markers^of apoptosis, i.e. 1) TUNEL staining and 2) caspase-8 and caspase-9 activation. This set of studies will enable us to determine: 1) how these three components of inflammation contribute to apoptotic cell death, 2) whether the intrinsic or extrinsic caspase pathways are involved, and 3) the neuroprotective mechanisms utilized by E2 to preserve the ischemic penumbra during stroke. Taken together, these studies will deepen our understanding of the complex neurprotective mechanisms employed by E2 in the adult and aging brain. Lay Summary After menopuase, the brain is particularly vulnerable to the long-term effects of hypoestrogenicity, as several studies have shown that low, physiological levels of 17beta-estadiol are capable of protecting the brain from injury and disease. Using a model of middle cerebral artery occlusion, these studies will determine the therapeutic effects of low, physiological levels of estradiol as a neuroprotectant from the multiple inflammatory stimuli that lead to programmed cell death of neurons during stroke. Completion of these studies will enhance our understanding of the complex ways that 17beta-estradiol protects during neurological injury.